3 isoforms of actin-

α - expressed only in muscle cells

β and γ - found together in almost all non-muscle cells

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#Unit 6. System Physiology – Plant

hy1 and hy2 mutant are chromophore biosynthesis mutant: which fail to supress hypocotyl elongation

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#Unit 6. System Physiology – Plant

Pfr is the physiologically active forms of Phytochrome

Wild type: short hypocotyl by white light

hy mutant (phytochrome mutant): long hypocotyl by white light

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#Unit 6. System Physiology – Plant

A toggle model is for phytochrome interconversion

The structure of the b-hairpin region of Pr is changed to an a helix during the conversion of Pr to Pfr, which initiates other conformational changes in the protein.

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#Unit 6. System Physiology – Plant

There are five phytochrome isoforms in angiosperms

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#Unit 6. System Physiology – Plant

PHYA is the only gene that encodes a Type I phytochrome and predominantly perceives far-red light.

Phytochrome B predominantly perceives red light

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#Unit 6. System Physiology – Plant

The PHYA gene is transcriptionally active in dark-grown seedlings, but its expression is strongly inhibited in the light in monocots.